The Clinical Core is the patient care and clinical research component of the proposed Program Project. It will relate to the Administrative Core for Administrative Core for administrative oversight and provide the clinical components needed for Projects 1 (Human fMRI Studies) and 2 (fMRI Development). It integrates into the Program the strengths of the existing drug abuse clinical research team, the extensive treatment facilities at the MGH Addiction Services, and the MGH Mallinkrodt General Clinical Research Center (GCRC). The existing clinical research team at the MGH currently conducts two NIDA-sponsored multi-year clinical trials (Buprenorphine Outpatient Treatment for Combined Opiate and Cocaine Dependence and the Cocaine Collaborative Psychotherapy Study). The MGH addictions treatment facilities include the CSAT-funded MGH Central Intake, an impatient detoxification and rehabilitation unit, a CSAT-initiated Day Treatment Program, and an outpatient addictions treatment clinic. The GCRC is a well-equipped and staffed dedicated inpatient research unit that has been funded by the NIH for over 30 years. It will contribute screening outpatient evaluation and impatient clinical management support, including medical and nursing care, physiologic monitoring, timed collection of body fluids and laboratory analysis. The Clinical Core is designed to manage all clinical aspects of the human experiments. These are four task areas: subject recruitment/characterization, subject preparation, subjective clinical measurement, and clinical safety. The specific tasks will be to: )1) recruit a sufficient sample of individuals who meet inclusion and exclusion criteria and provide a reliable and valid characterization of these individual's cocaine exposure, pattern and diagnostic status, (2) to prepare subjects so that they comprehend study procedures and are able to comply with study procedures and be retained for follow-up readmission, (3) to obtain reliable and valid experimental subjective measures and (4) to safely care for subjects following the imaging experiments by closely monitoring them in a medical unit, by counseling subjects to perceive the study experience as an educational process and by facilitating treatment engagement and safe discharge.